Foundry composition with cross-linked polyester binder



April 27, 1965 s. E. FREEMAN 3,179,990

FOUNDRY COMPOSITION WITH CROSS-LINKED POLYESTER BINDER Filed Oct. 26.1961 JIIIIII'I a I I 6'5 7 I /5 R067? 07". i i J76 lrerz'lf'eama/zUnited States Patent 3,17%990 FUUNDRY COMPOSITION WITH CROSS-LINKEDPOLYESTER BINDER Stephen E. Freeman, Mequon, Wis, assignor to Freeman(Jhemical Corporation, Port Washington, Wis, a corporation of DelawareFiled Get. 26, 1961, Ser. No. 147,857 12 Qlaims. (Cl. 22-194) Thisapplication is a continuation-in-part of my copending application SerialNo. 636,434, filed January 25', 1957, now abandoned.

This invention relates to compositions, methods, and apparatus for theproduction of foundry cores.

In casting metal objects having a cavity, a foundry core may bepositioned in the mold, Which core, during the pouring of molten metalinto the mold, occupies and thus forms the final cavity.

Foundry cores may be conventionally produced by mixing refractory coresuch as core sand mixtures and molding sand With a binder such as dryingoils, as exemplified by linseed oil, or thermosetting resins such asurea-formaldehyde, phenol-formaldehyde and melamine-formaldehyde. Therefractory-binder mix may then be shaped into the desired form andheated or baked at elevated temperatures which may reach as high as 250to 600 F. in order to dry the oil or cure the resin, thus enabling therefractory material to be bound together by'the binder into a rigidstructure which will not collapse in the mold before the molten metalfreezes or sets." If desired, cereals such as dcxtrin and starch mixedwith water may be added to the refractory material and conventionalbinders in order to enable the shaped core to develop green strength sothat it maintains its shape and does not crumble prior to theapplication of heat in the baking step. t

The application of heat to induce or facilitate the drying or curing ofthe binder and hardening of the mix requires the use of costly andspace-consuming equipment such as ovens.

The use of a particular binder with foundry refractory material to makefoundry cores is a highly specific use which requires that the resultingcore have particular characteristics which are not generally associatedWith refractory-binder or filler-binder mixes used in other arts. Forexample, the ideal foundry core mix (i.e., refractory material plusbinder) should (1) remain plastic sutliciently long to permit shaping ofthe core, (2) develop green strength within a reasonable period of time,preferably at room temperature, so that the shaped core will maintainits shape prior to and during baking, (3) reach high tensile strengthvalues, (4) permit molten metal to be poured against the hardened core(e.g., baked cores) Without undergoing distortion or excessive gassing,(5) enable the hardened core to be permeable so as to permit gases to beevolved therefrom during the casting operation, and (6) enable thehardened core to readily collapse after the molten metal has set. Theseare stringent requirements.

My invention contemplates the use of compositions, methods, andapparatus which do not necessitate the application or utilization ofheat in order to produce a core Which develops, in a comparatively shortperiod of time, suflicient tensile strength and scratch hardness valuesso as to enable the core to maintain its shape whenmolten metal ispoured against it and collapse after the metal freezes or sets. The corewill undergo continuous curing up to the time these values are reachedand Will rapidly develop green strength during this curing cycle;however, green strength is only an intermediate, transistory conditiondeveloped during the curing cycle.

ICC

My invention includes the production of foundry cores (e.g., Withoutnecessitating the application of heat) by bonding particulate refractoryfoundry core material with a binder system to form a curable mix. Thecurable binder system comprises (a) a resin mix having therein anethylenically unsaturated polyester formed from the reaction of anunsaturated alpha-beta ethylenically unsaturated polycarboxylic acidwith a polyhydric alcohol, and a monomeric ethylenically unsaturatedpolymerizable cross-linking agent, (11) a per-oxidizing polymerizationcatalyst such as an acyl peroxide or hydroperoxide, (c) a polymerizationaccelerator in the form of a metallic drier or organic salt when theperoxide catalyst is not an acyl peroxide such as benzoyl or lauroylperoxide, and (d) an amine polymerization promoter that is free of nitroor nitroso groups. When an amine polymerization promoter is used in thevapor phase, it should be the last of said members of said binder systemthat is added to the curable mix.

The curable mix produced will develop tensile strength values up to150400 p.s.i., and above, as determined by an H. W. Dietert sandstrength machine. In addition, the curable mix Will develop hardnessvalues up to -90, and above, as determined by an H. W. Dietert dryhardness tester No. 673. Cured cores may be immediately used in castingboth high and low temperature molten metal such as molten iron, steel,aluminum, brass, magnesium, and the like.

The ethylenically unsaturated polyester resin is the polymerizedreaction product of at least one polyhydric alcohol and at least oneunsaturated polycarboxylic acid or anhydride thereof. The reactionproduct may be formed by heating alpha-beta ethylenically unsaturateddicarboxylic acids such as maleic, fumaric, and their anhydrides With apolyhydric' alcohol or a glycol such as ethylene glycol, diethyleneglycol, propylene glycol, polyethylene glycol, polypropylene glycol, and1,3 butylene glycol. Unsaturated tricarboxylic acid or -anhydride, suchas trimellitic anhydride, may also be used. It is essential that some ofthe polycarboxylic acid component of the polyester resin contain anunsaturated ethylenic linkage.

The relatively volatile, ethylenically unsaturated compound has thegroup CH :C and serves to render the unsaturated polyester resin lessviscous and to crosslinlc said resin during curing so as to produce acrosslinked or S-dimensional resin which is thermosetting in character.Cross-linking agents such asexemplified by styrene, vinyl toluene, vinylacetate, and diallyl esters (e.g., diallyl phthalate) may be used.

The peroxide, peroxidic or per-oxidizing polymerization catalysts shouldbe solublein the aforesaid polymerizable mixture and must be capable ofinducing polymerization of said mixture in the presence of refractorymaterial at temperatures below about C. or, preferably, between 2040 C.Peroxides or organo-peroxidizing agents'such as acyl peroxide andhydroperoxide have been found to'be particularly effective. For example,

good results are obtained with diacyl peroxides such as solution ofcobalt naphthenateKcontaining 6% cobalt) in naphtha may be used.

The amine polymerization promoter must be free of nitro or nitrosogroups and have a boiling point sufiiciently low so as to volatilizewithout undergoing decomposition in the presence of the refractorymaterial and other members of the polymerizable mixture at temperaturesbelow about 125 C. or, preferably, between 20-40 C. The promoters of thepresent invention markedly accelerate or promote the polymerization ofthe polymerizable mixture at temperatures up to 250 C. in the presenceof refractory material. Particularly good results are obtained withN,N-dialkyl aryl tertiary monoamines such as dimethylaniline,diethylaniline, N,N-dimethyl-p-toluidine and N,N-dimethyl-o-toluidine.

If desired, hydroquinone and p-tertiary butyl catechol may beincorporated into the polymerizable mixture as inhibitors andstabilizers. For example, hydroquinone may be present with thepolyhydric alcohol and unsaturated dicarboxylic acid or anhydridethereof during the formation of the unsaturated polyester resin, and thep-tertiary butyl catechol inhibitor may be added to the unsaturatedpolyester resin along with the ethylenically unsaturated crosslinkingcompound. Care should be exercised so as to avoid the use of excessivelyhigh levels of inhibitors and stabilizers in order to obviate anexcessive reduction in the polymerization activity of the polymerizablemixture.

The terms refractory material or refractory foundry material areintended to refer to unused and/ or reclaimed, non-deleteriousrefractory material which may be admixed with members of thepolymerizable mixture so as to produce a curable mix which may be shapedand hardened sufiiciently, so as to produce a core having a desirabletensile strength value, without necessitating the application of heat.Thus, these phrases are intended to include conventional washedrefractory materials such as exemplified by washed crude alumina,silicas and clays. For example, zircon sands, Ottawa sand, andMississippi sand from Rockford, Illinois, produce satisfactory cores.The refractory material should be free of any deleterious materialswhich tend to interfere with the effective curing of the polymerizablemixture. The most effective results are obtained with dry refractorymaterial.

A core which is suitable for casting metals may be formed, for example,by a method comprising: mulling refractory foundry core material with apolymerizable accelerator in the form of a metallic drier or organicsalt, thereby coating the refractory material; adding to the coatedrefractory material a pre-mix comprising a resin mix having therein anethylenically unsaturated polyester and cross-linking agent, and asoluble per-oxidizing polymerization catalyst such as a hydroperoxide;mulling the resulting mix to form the first mulled mix; passing thefirst mulled mix through an amine mixing zone so as to uniformly admixthe first mulled mix with an amine promoter (i.e., in the vapor phase)and/or a second mulled mix comprising an admixture of a relatively smallamount of refractory material and amine polymerization promoter, to forma curable mix; packing the curable mix into a core box so as to form ashaped curable mix that will rapidly develop green strength (e.g.,without necessitating the application of heat); and permitting theshaped core to develop suflicient tensile strength and scratch hardnessvalues as to enable the core to maintain its shape when molten metal ispoured against it and collapse after the metal freezes or sets. If oneuses an acyl peroxide such as benzoyl peroxide or lauroyl peroxide, saidpolymerizable accelerator should be omitted.

Other procedures, of course, may be used. For example, the first mulledmix may be packed or blown into the core box, and the aminepolymerization promoter, in the vapor phase, may be blown into the firstmulled mix in the core box by means of air so as to promptly initiate orcause the shaped curable mix to harden.

If desired, a portion of the accelerator may be incorporated into thepre-mix and added therewith to the mixture of refractory material andremaining portion of accelerator. The peroxidic catalyst may be directlyadmixed with the refractory material and accelerator; however, extremecare should be exercised so that the peroxidic catalyst is not directlyadmixed with the accelerator.

The rapid development of said green strength is a transistory,intermediate condition which occurs during curing, but prior to thedevelopment of scratch hardness and tensile strength values that permitmolten metal to be poured against the core.

The amine polymerization promoter should not be stored in the presenceof the peroxidic catalyst or polymerizable mixture of the unsaturatedpolyester resin and cross-linking agent because a reduction in the rateof curing of the curable mix results. The promoter should be,preferably, the last ingredient added to the curable mixture.

The internal confines of the core box may be coated with aparting-agent, such as starch or a lubricating oil, for facilitatingremoval of a shaped core from the core box.

The curable mixes of some of the following examples were prepared fortest purposes only and were not prepared in complete conformance withthe above-described procedure. When the following examples state thatthe curable mix hardened or is hard, the mix has developed a tensilestrength value that is sufficiently high to permit molten metal to beimmediately poured against it.

EXAMPLE I The polymerizable mixture of unsaturated polyester resin andethylenically unsaturated monomer may be prepared as follows:

A mixture of 15.10 parts by weight phthalic anhydride, 10 parts byweight maleic anhydride, 18.54 parts by weight propylene glycol, and0.004 part by weight of hydroquinone may be heated to 200 F. in a closedvessel under carbon dioxide gas or other inert atmosphere. Theapplication of heat should be discontinued and the reaction permitted toexotherm to 300-320 F. The reaction mixture may then be heated slowly to400 F. and the evolution of the water of esterification effected. Afterthe reaction mixture attains an acid value of 33-35, the application ofheat should be discontinued and the reaction mixture permitted to coolto 220 F. The resulting product is an unsaturated polyester resin.

20 parts by weight of vinyl toluene solvent and 0.004 part by weight ofp-tertiary butyl catechol may be added to the polyester resin while theresin is being agitated at about 220 F. The resulting polymerizablemixture should be cooled to at least 130 F. for storage.

This polymerizable mixture of unsaturated polyester resin-ethylenicallyunsaturated cross-linking monomer may be stored for at least six monthsat F.

EXAMPLE II The same procedure and ingredients set forth in Example I maybe used, with the exception that styrene monomer may be substituted forthe vinyl toluene monomer.

' EXAMPLE III A curable mix of refractory material and polymerizablemixture was prepared for test purposes in accordance with the followingprocedure, although said procedure does not conform with my preferredmethods of preparing curable mixes and cores setforth, supra:

4000 gm. of dry Ottawa sand (A.F.S.--47) were placed in a mixer. Mixingof the refractory material was effected while 3.3 gm. of 50% dimethylaniline promoter in varnish makers and painters naphtha, hereinafterreferred toas naphtha, was added in a thin stream to the sand. 8.3 gm.of 50% solution of 6% cobalt naphthenate in naphtha (i.e., cobaltnaphthcnate containing 6% cobalt .is admixed with naphtha to form a 50%solution) was added to and mixed with the sand and promoter.

5 The polymerizable mixture was prepared by (a) adding 2.1 ml. of 50%methyl ethyl ketone peroxide in dimethyl phthalate to 165 gm. of thepolymcrizable mixture of Example II, (b) thoroughly mixing thisadmixture, (c) addwere then added to and mulled with the drier-sand mixfor 3 minutes; the resulting curable mix was then packed into threepaper drinking cups so as to form three core samples.

ing drops of a solution of cobalt naphthenate in naphtha, 5 After twosamples were cured for 2 and 5 minutes, reand (d) mixing the resultingproduct. spectively, they were removed from their respective cups.

This polymerizable mixture was added in a steady The core that cured for2 minutes was capable of supstream to the promoter-sand mix and theresulting eurporting a l-pound weight without slumping; and when ablemix was stirred thoroughly for 4-5 minutes, packed an 8-pound weight wasplaced on top of the core that was into a mold, and tamped. The masshardened in 5 to 1O cured for 5 minutes, the core slumped slightly. Thethird minutes, sample was removed from its cup after being cured over-EXAMPLE IV night; this-core was uniformly very hard. The effect ofvarious levels of p-tertiary butyl catechol EXAMPLE VI i rate of Cunngof the curable mm shown In Table 15 0.3 ml. of 50% cobalt naphthenate(containing 6% in racobalt) in naphtha is admixed with 97 gm. of OttawaPdymtnzable Mlxture A W Prepared by admlmg= sand (A.F.S.47). 0.1 ml. ofN,N dimethyl-p-toluidine 4O of 3 g fig 3 Elxample Supra and 3 gm. of amixture of 80 parts by weight of the polym- 00 age on t e h t e styrenemonomer erizable mixture of Example I, 1 part by weight of 60% ofptfmtmry butyl Catechol mhibltor 9 banzoyl 2O methyl ethyl ketoneperoxide in dimethyl phthalate, and peroxide, and 0.3 ml. of 10%dimethyl aniline 111 ElC6tOl'16. 1'6 parts by Weight of 50% benzoylperoxide in an inert Polymenzable Mlxture B and polynlerlzafk Muitm'e Csolvent (e.g., dimethyl phthalate) are then added to and 5 i gi i i g ig g; li i gg 2, mulled with the drier-sand mix for a few minutes. The

O ymsnza e w e e n a 0 resultin' curable mix ma then be acked int and0.05%, respectively, of the inhibitor (based on the Cup a y p O a paperStyrsne monomer), were composifian of each The curable mix will be hardin about 2 minutes and of these polymerizable mlxtures is shown in TableI, uniformly wry hardin minutes infra.

Table II shows the relative curing rates of (a) Polym- EXAMPLE VIIerflflblfi MIIftQYeS and P 53 1 Fumble When 0.1 ml. of N,Ndimethyl-o-toluidine is substituted mixes containing each of saidpolymerizable mixtures, 30 f N,N dimethyl-p-toluidine in Example VI, acurable dlmethyl $111916 pl'ometer and 9 mix is formed that cures at thesame rate as the curable tor. The rate of curing was found to bedirectly propori f E k 1 tional to the level of inhibitor contained inthe polymerizable mixture (i.e., curing rates (expressed in time) ofEXAMTLJLE VIII the polymerizable mixtures and curable mixes increasedPolymerizable Mixtures E, F, G, and H were prepared when increasedlevels of inhibitor were used). by admixing the solvent-free,unsaturated polyester resin Table I POLYMERIZABLE MIXTURES PolymerizablePolymerizable Polyruerizable Mixture A Mixture B Mixture C (Jumblemixture of Example II 40 gm 40 gm 40 gm.

15.1 parts by weight phthalie auhydride. 10 parts by weight maleie an-(Contains (Contains (Contains hydri e. 0.0l25% p- 0.025% pi 0.05% p-18114 parts by weight propylene tertiary butyl tertiary butyl tertiarybutyl glycol. eatechol based eatechol based eatechol based 20 parts byweight styrene on styrene.) on styrene.) on styrene.)

IDOHOIHBI. I Benzoyl peroxide 0.4 urn 0.4 m 0,4 gm, 10% dimethyl anilinein acetone; 0.3 ml 0.3 m1 0.3 ml.

Table II C U RAB LE MIX Ingredients Sample 1 Sample 2 Sample 3Polymerizable Mixture A. 4 gm. (hard in 20 min)" Polymerizable Mixture B4 gm. (hard in 1 hr.) Polyinerizable Mixture 0.- 4 gm. (hard in 4 hrs).10% dimethyl aniline in ace- 0.5 ml 0.5 ml 0.5 m1.

tone. 10% solution of cabalt naph- 1. 5 ml. 1. 5 ml 1. 5 m1.

thenate (6% cobalt) in naphtha. Ottawa Sand (A.F.S.-47) 96 gm 96 gm 96gm. Curing rate of curable mix Hard in 10 min. Cured Hard in 15 min Hardin 4 hrs.

so rapidly that sand was not bound uniiormly.

EXAMPLE V (100% total solids) of Example I with a combination 015 ofcobalt naphthenate (containing 6% cobalt) 70 of reactive solventscomposed of vinyl toluene and inin naphtha was admixed with 97 gm. ofOttawa sand (A.F.S.47). 0.2 ml. of 50% dimethyl aniline in naptha and 3gm. of a mixture of 40 parts by weight of the polymerizable mixture ofExample I and 0.5 part by weight of creasing levels of divinyl benzenein the amounts shown ,in Table III, infra.

These polymerizable mixtures were then admixed with the ingredients setforth in Table IV, infra, in the amounts methyl ethyl ketone peroxide indimethyl phthalate therein shown so as to form curable mixes which were7 rapidly shaped into cores. Table III and Table IV show that as thepercentage of divinyl benzene in the total amount of reactive thinner isincreased, the tendency of the cured or hardened core to soften upon theapplication of heat thereto decreases.

Table III POLYME RIZABLE MIXTURE s Commercial grade divinyl benzenecontains 50-60% divinyl benzene diluted with ethyl vinyl benzene andabout of inert solvent such as ethyl benzene and the like.

curing the mix overnight. Cores containing about 6-7% dimethyl aniline(based on the polymerizable mixture of Example I) cure so rapidly thatit is difficult to get a uniform curable mix before a portion of the mixcures in the form of lumps. Cores containing more than about dimethylaniline (based on the polymerizable mixture of Example I) do not cureinto hard cores; this indicates that excess promoter may actually retardcuring.

Thus, the rate at which a hard core is formed with dimethyl anilinepromoter (based on the unsaturated polyester resin plus cross-linkingagent) is directly proportional to the level of promoter used when themix contains about 0.33% to about 6% promoter; when more than about 7%promoter is used, the curing rate is inversely proportional to the levelof promoter in the mix.

EXAMPLE X The following procedure may be used to show the effect ofvarious levels of cobalt (based on the polymerizable mixture ofunsaturated polyester resin plus crosslinking agent of Example I), inthe form of cobalt T able IV EFFECT OF DIVINYL BENZENE ON REDUCTION OFHEAT SOFTENING Ingredients Sample 1 Sample 2 Sample 3 Sample 4Polymerizable Mixture A Polymerizable Mixture B Polymerizable Mixture CPolymerizable Mixture D.-.

Ottawa sand (A.F.S.-47) 291 g 291 g Cobalt naphthenate (contain 0.45 ml6% cobalt).

Dlmethyl aniline 0.3 ml 0.3 m1

60% methyl ethyl ketone perox- 0.15 ml 0.15 ml ide in dimethylphthalate- Time required for curable mix 5 minutes. 5 minutes 5 minutes5 minutes.

to become hard.

t distortion (on hot plate) Less thermoplastle More rapid reset Lessthermoplastic 261m. after formation of curthan Sample 1. than Sample 2.than Sample 2.

Heat distortion (on hot late) Less thermoplastic More rapid reset Lessthermoplastic 24 hrs. after formation of (am than Sample 1. than Sample2. than Sample 2. able mix.

EXAMPLE IX naphthenate, on the curing characteristics of the curable Thefollowing procedure may be used to show the effect of various levels ofdimethyl aniline promoter (based on a polymerizable mixture of anunsaturated polyester resin plus cross-linking agent) on the curingcharacteristics of the curable mixes:

A polymerizable mixture is prepared by admixing (a) 1 part by weight ofmethyl ethyl ketone peroxide in dimethyl phthalate and 1.6 parts byweight of 50% benzoyl peroxide in an inert solvent (e.g., dimethylphthalate) with (b) 80 parts by weight of the polymerizable mixture ofExample I.

97 gm. of Ottawa sand (A.F.S.-47) are placed in a mixer. The mixer isstarted, and the desired level of dimethyl aniline is added to the sand.0.3%, based on the weight of the polymerizable mixture of the polyesterresin and cross-linking monomer of Example I, cobalt in the form ofcobalt naphthenate is added to the mixer and mulled with the sand andpromoter.

Said polymerizable mixture is then added in a steady stream to thecontents of the mixer and the resulting curable mix is rapidly, butthoroughly, mixed. The core is then formed.

Curable core mixes produced in this manner will have the followingcuring characteristics:

The most rapid effective cures (at room temperature) occur with corescontaining about 1 to about 5% dimethly aniline (based on thepolymerizable mixture of Example I). When about 1% down to about 0.33%of dimethyl aniline (based on the polymerizable mixture of Example I) isused, a hard core is obtained only after A polymerizable mixturecontaining methyl ethyl ketone peroxide, benzoyl peroxide and thepolymerizable mixture of Example I is prepared in accordance with theprocedure set forth in Example IX.

97 gm. of Ottawa sand (A.F.S.47) are placed in a mixer. The mixer isstarted and 3.3% dimethyl aniline (based on the polymerizable mixture ofExample I) is added to the sand. Various percentage levels of cobalt(based on the Weight of the polymerizable mixture of Example I) in theform of cobalt naphthenate are added to the mixer and mulled with thesand and promoter.

Said polymerizable mixture is then added in a steady stream to thecontents of the mixer and the resulting curable mix is rapidly, butthoroughly, mixed.

Curable core mixes produced in the manner referred to in Example X willhave the following curing characteristics:

The most rapid cures (at room temperature) occur with cores containingabout 1% cobalt (based on the polymerizable mixture of Example I) whichhas been added as cobalt naphthenate. Curable mixes containing at leastabout 0.0250.03% cobalt (based on the polymerizable mixture of ExampleI) produce cores that are fairly hard after an extended number of hours.When about 0.07%, 0.1%, and 1% cobalt (based on the polymerizablemixture 'of Example I) are used, hard cores are produced in about 5minutes, 2 minutes, and instantaneously, respectively. When about 2%cobalt (based on Q the polymerizable mixture of Example I) is used, thecore hardens in about 2 minutes.

The rate at which a hard core is formed with cobalt (based on thepolymerizable mixture of Example I), in the form of cobalt naphthenate,is directly proportional with the level of cobalt used when the mixcontains about 0.025% to about 1% cobalt; when more than about 1% cobaltis used, the curing rate is inversely proportional to the level ofcobalt in the mix. Excessive levels of cobalt may, thus, actually retardcuring. Effective results may be obtained with about 0.025% to 3% cobalt(added as a drier), based on the unsaturated polyester resin pluscross-linking agent; however, the use of about 0.5% to 1% cobalt (addedas a drier), based on the unsaturated polyester resin plus cross-linkingagent, is preferred.

Today, foundry cores are being produced by machines which blow therefractory material and binder into the core mold with a blast of air.The binder serves to lend green strength to the core so that it may beremoved from the mold after it has been shaped. The core may then bebaked so that it develops sufficient tensile strength so as to enablethe core to maintain its shape When molten metal is poured against it;the core should collapse after the metal freezes or sets.

FIGURE 1 is a diagrammatic'drawing of apparatus which may be used toproduce curable mixes, with the above-described components, whichrapidly develop green strength and suihcient tensile and scratchhardness values without necessitating the application of heat.

PTGURE 2 is an enlarged diagrammatic view of the core box shown inFIGURE 1.

Refractory material may be suitably mulled with a polymerizable mixturecontaining an unsaturated polyester resin, ethylenically unsaturatedcross-linking monomer, peroxidic polymerization catalyst anddrier-accelerator to form a mix 4-0 which may be placed in the reservoir21L Column 12 should be packed with a suitable absorbent 41, such assteel wool, which has been soaked with the amine promoter.

Valves Ill, 14, and 249 should be opened and compressed air (at 90p.s.i.) introduced into the system through air pipe 10. The air pressurewill force the mix 40 through openings 22 in reservoir 21 into mixingzone 30 and through a stream of promoter vapor which has been forced bythe compressed air from column 12 into the mixing Zone 30. The curablemix (i.e., refractory material and polymerizable mixture of unsaturatedpolyester resin, cross-linking agent, peroxidic catalyst, promoter, anddrier-accelerator) will be forced through the opening 31 in mixing zone30 into the core box 3'2.

The curable mix will enter the core box 32; through blow hole 33 andwill be packed into the core cavity 35 of the mold 42 onto a screen aswhich is positioned above the opening 37 at the bottom of the core box.Air may escape from the core box through the creen 36 as Well as throughthe screened vent 34.

The curable mix will harden in about one minute so it will have sumcientgreen strength to stand without collapsing. After about 1-2 minutes ormore at room temperature, the mix will uniformly and thoroughly hardento develop suflicient tensile strength so as to enable molten metal tobe poured against it; in the event that low levels of aminepolymerization promoter are used, the time required for the mix toharden will be increased. Mild heat will accelerate the development ofthis tensile strength.

If desired, values lit and 14 may be closed and valve 20 left open sothat compressed air (90 p.s.i.) entering the system through pipe willforce the mix 40 into the cavity 35 of the core box 32. Valve shouldthen be closed and valves 11 and M opened so as to enable the promoterto be forced into the core box through blow hole 33 and through the mix40.

t0 EXAMPLE XI The mix 4%) shown in FIGURE 1 may be prepared by (a)mulling 970 gm. of Ottawa sand (A.P.S.-47) with 3.0 ml. of 50% solutionof cobalt naphthenate (containing 6% cobalt) in naphtha, (b) adding apolymerizable mixture containing 30 gm. of the polymerizable mixture ofExample II, 0.37 gm. of 50% methyl ethyl ketone peroxide in dimethylphthalate, and 0.60 gm. of 50% benzoyl peroxide in dimethyl phthalate tothe acceleratorsand mix, and (c) mulling the resulting mix 4%. When themix 40 is combined with 1-3 gm. of dimethyl aniline .vapor, a curablemix is formed that will develop sufiicient tensile strength values onabout 1-2 minutes so as to permit molten metal to be poured against it.

As pointed out above, care should be exercised in selecting the level ofpromoter and drier-accelerator because excessive levels of thesecomponents, like insufficient levels, may serve to extend the timerequired for the core to reach tensile strength values which permitmolten metal to be poured against it, or entirely inhibit thedevelopment of such values.

Effective curing of the curable mix may be obtained when thepolymerizable mixture of unsaturated polyester resin plus cross-linkingagent contains about 67% polyester resin and about 33% monomericcross-linking agent. (The proportions referred to, infra, are based uponpolymerizable mixtures containing approximately this proportion, orequivalent proportions, of polyester resin plus cross-linking agent.)

Suitable curable mixes for core use which rapidly develope tensilestrength and hardness values sufiicient for casting purposes may beprepared With about 0.5% to 6% by weight of a polymerizable mixture ofunsaturated polyester resin plus cross-linking monomer and about99.5%94% by weight refractory material. However, I prefer to use curablemixes having about 2-4% by weight polymerizable mixture of unsaturatedpolyester resin plus cross-linking monomer and 9896% by weightrefractory material. When more than about 6% polymerizable mixture ofunsaturated polyester resin plus crosslinking monomer is used with about94% refractory material, dense, hard cores will be produced which do notpossess suiiicient gas permeability properties. These percentages arebased on the weight of the unsaturated pollyester resin, cross-linkingagent, plus refractory materia The relative proportion of peroxidiccatalyst used in my curable mix is not particularly critical. Forexample, about 0.34%, or higher, catalyst (based on the unsaturatedpolyester resin plus cross-linking agent) may be used; however, curablemixes containing about 1.02.0% catalyst (based on the unsaturatedpolyester resin plus cross-linking agent) are particularly effective.Excessively high levels of peroxidic catalyst tend to produce brittlecores which possess poor tensile strength values.

Metal-containing accelerators, such as cobalt driers, may be present inthe curable mix in the range of about 0.0253% metal (added as a drier)based on the unsaturated polyester resin plus cross-linking agent;however, curable mixes containing a cobalt drier as an ac celeratorshould, preferably, contain about 0.5-l.0% cobalt (added as a drier)based on the unsaturated polyester resin plus cross-linking agent. Asindicated in Example X, excessively high levels of cobaltdrieraccelerator may serve to retard curing of the curable mix, orprevent curing of the mix.

Promoters, such as dimethyl aniline, may be present in the curable mixin the range of about 0.l86%, preferably about 1-5%, based on theunsaturated polyester resin plus cross-linking agent. As indicated inExample IX, excessively high levels of dimethyl aniline may serve toretard curing of the curable mix, or prevent curing of the mix.

1 ll For example, the following formulations exemplify suitable curablemixes (the term part and parts refer to part or parts by weight) 99.5-94parts refractory material.

0.5-6 parts polymerizable mixture of the type illustrated in Examples Iand II.

0.0025 or more part peroxidic catalyst.

000165-036 part amine promoter such as dirnethyl aniline.

0.00015-0.18 part metal accelerator such as cobalt in the form of cobaltnaphthenate.

The percentage values expressed in the claims are intended to be on aweight basis. The term up to in the claims excludes zero. The term resinmix in the claims includes the polyester resin and cross-linking agent.

The foregoing detailed description has been given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, as modifications will be obvious to those skilled in the art.

I claim:

1. The method of producing foundry structures which comprises: forming afoundry core mix with a mixture of about 99.594% of refractory foundrymaterial and up to about 6% of polymerizable resin mix containingethylenically unsaturated polyester resin formed from the reaction of anunsaturated polycarboxylic acid and polyhydric alcohol and monomeric,ethylenically unsaturated, polymerizable cross-linking agent, at leastabout 0.8% of peroxide polymerization catalyst that is soluble in saidresin mix, a polymerization accelerator when said catalyst does notinclude acyl peroxide, said accelerator being in the form of a solubleorganic salt which provides at least about 0.025% metal in an activestate that induces acceleration of the polymerization of said resin mix,and at least about 0.18% of vapor phase N,N-dialkyl tertiary monoaminepolymerization promoter free of nitro and nitroso groups, said promoterbeing introduced in the vapor phase to form a hardenable foundry coremix that hardens into a hard, self-supporting, porous foundry coreagainst which molten metal may be poured and shaped before said coreundergoes distortion or collapses, said percentages of refractorymaterial and resin mix being based on said refractory material plus saidpolymerizable resin mix, the percentages of said catalyst, metal andpromoter being based on said resin mix.

2. The method of producing foundry cores as defined in claim 1 whereinsaid catalyst is selected from the group consisting of benzoyl peroxide,lauroyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide andt-butyl hydroperoxide, said accelerator is selected from the groupconsisting of cobalt naphthenate, cobalt octoate, manganese naphthenateand manganese octoate, and said promoter is selected from the groupconsisting of dimethylaniline, diethylaniline, N,N-dimethylp-toluidineand N,N- dimethyl-o-toluidine.

3. The method of producing foundry structures which comprises: forming afoundry mix with a mixture of about 99.594% of refractory foundrymaterial and up to about 6% of polymerizable resin mix containingethylenically unsaturated polyester resin formed from the reaction of anunsaturated polycarboxylic acid and polyhydric alcohol and monomeric,ethylenically unsaturated, polymerizable cross-linking agent, at leastabout 0.3% of a hydroperoxide polymerization catalyst that is soluble insaid resin mix, a polymerization accelerator in the form of a solubleorganic salt which provides at least about 0.025% metal in an activestate that induces acceleration of the polymerization of said resin mix,and at least about 0.18% of vapor phase N,N-dialkyl tertiary monoaminepolymerization promoter free of nitro and nitroso groups, said promoterbeing introduced in the vapor phase, to form a hardenable foundry coremix that hardens into a hard, self-supporting, porous foundry coreagainst which 2. molten metal may be poured and shaped before said coreundergoes distortion or collapses, said percentages of refractorymaterial and resin mix being based on said refractory material plus saidpolymerizable resin mix, the percentages of said catalyst, metal andpromoter being based on said resin mix.

4. The method of producing foundry structures which comprises: forming afoundry mix with a mixture of about 99.594% of refractory foundrymaterial and up to about 6% of polymerizable resin mix containingethylenically unsaturated polyester resin formed from the reaction of anunsaturated polycarboxylic acid and polyhydric alcohol and monomeric,ethylenically unsaturated, polymerizable cross-linking agent, at leastabout 0.3% of an acyl peroxide polymerization catalyst that is solublein said resin mix, and at least about 0.18% of vapor phase N,N-dialkyltertiary monoamine polymerization promoter free of nitro and nitrosogroups, said promoter being introduced in the vapor phase, to form ahardenable foundry core mix that hardens into a hard, self-supporting,porous foundry core against which molten metal may be poured and shapedbefore said core undergoes distortion or collapses, said percentages ofrefractory material and resin mix being based on said refractorymaterial plus said polymerizable resin mix, the percentages of saidcatalyst and promoter being based on said resin mix.

5. The method of producing foundry cores which comprises: forming ahardenable foundry core mix with a mixture of about 99.5-94 parts byweight of refractory foundry core material, about 0.5-6 parts by weightof polymerizable resin mix containing ethylenically unsaturatedpolyester resin formed from the reaction of an unsaturatedpolycarboxylic acid and polyhydric alcohol and monomeric, ethylenicallyunsaturated, polymerizable cross-linking agent, and, based on the weightof said polymerizable resin mix, at least about 0.3% of a hydroperoxidepolymerization catalyst that is soluble in said resin mix, apolymerization accelerator in the form of a soluble organic salt whichprovides about 0.0253% metal in an active state that inducesacceleration of polymerization of said resin mix, and about 0.186% ofvapor phase N,N-dialkyl tertiary monoamine polymerization promoter freeof nitro and nitroso groups, said promoter being introduced in the vaporphase, to form a hardenable foundry core mix that hardens into a hard,self-supporting, porous foundry core against which molten metal may bepoured and shaped before said core undergoes disstortion or collapses.

6. The method of producing foundry cores which comprises: forming ahardenable foundry core mix with a mixture of about 99'.594 parts byweight of refractory foundry core material, about 0.5-6 parts by weightof polymerizable resin mix containing ethylenically unsaturatedpolyester resin formed from the reaction of an unsaturatedpolycarboxylic acid and polyhydric alcohol and monomeric, ethylenicallyunsaturated, polymerizable cross-linking agent, and, based on the weightof said polymerizable resin mix, at least about 0.3% of an acyl peroxidepolymerization catalyst that is soluble in said resin mix, and about0.l86% of vapor phase N,N-dialkyl tertiary monoamine polymerizationpromoter free of nitro and nitroso groups, said promoter beingintroduced in the vapor phase, to form a hardenable foundry core mixthat hardens into a hard, self-supporting, porous foundry core againstwhich molten metal may be poured and shaped before said core undergoesdisortion or collapses.

7. The method of producing foundry cores which does not necessitate theuse of heat comprising: admixing up to about 6% of polymerizable resinmix containing ethylenically unsaturated polyester resin formed from thereaction of unsaturated polycarboxylic acid and polyhydric alcohol andmonomeric, ethylenically unsaturated, polymerizable cross-linking agent,and at least about 0.3% of hydroperoxide catalyst with an admixture ofrefractory foundry core material and polymerization accelerator in theform of a soluble organic salt that provides at least about 0.025% metalin an active state that serves as a polymerization accelerator; andadding to and admixing with the resulting admixture at least about 0.18%of a vapor phase N,N-dialkyl tertiary monoamine polymerization promoterfree of nitro and nitroso groups to form, without necessitating the useof heat, a hardenable foundry core mix having about 99.594% ofrefractory material and that hardens into a hard, self-supporting,porous foundary core against which molten metal may be poured and shapedbefore said core undergoes distortion and collapses; said percentages ofsaid resin mix and said refractory material being based on the totalweight of those materials and the remaining percentages being based onsaid resin mix.

8. The method of producing foundry cores which does not necessitate theuse of heat comprising: admixing up to about 6% of polymerizable resinmix containing ethylenically unsaturated polyester resin formed from thereaction of an unsaturated polycarboxylic acid and polyhydric alcoholand monomeric, ethylenically unsaturated, polymerizable cross-linkingagent, and at least about 0.3% of acyl peroxide catalyst with refractoryfoundry core material; and adding to and admixing With the resultingadmixture at least about 0.18% of a vapor phase N,N-di alkyl tertiarymonoamine polymerization promoter free of nitro and nitroso groups toform, Without necessitating the use of heat, a hardenable foundry coremix having about 99.5-94% of refractory foundry material and thathardens into a hard, self-supporting, porous foundry core against whichmolten metal may be poured and shaped before said core undergoesdistortion and collapses; said percentages of said resin mix and saidrefractory material being based on the total weight of those materialsand the remaining percentages being based on said resin mix.

9. The method of producing foundry cores which does not necessitate theuse of heat comprising: admixing up to about 6% of polymerizable resinmix containing ethylenically unsaturated polyester resin formed from thereaction of an unsaturated polycarboxylic acid and polyhydric alcoholand monomeric, ethylenically unsaturated, polymerizable cross-linkingagent, and at least about 0.3 of hydroperoxide catalyst with anadmixture of about 99.594% of refractory foundry core material andpolymerization accelerator in the form of a soluble organic salt thatprovides at least about 0.025% metal in an active state that serves as apolymerization accelerator; packing the resulting admixture into a corebox; and propelling at least about 0.18% of a vapor phase N,N-dialkyltertiary monoamine polymerization promoter free of nitro and nitrosogroups into said resulting admixture to form a hardenable foundry coremix that hardens at room temperature into a hard, self-supporting,porous foundry core against which molten metal may be poured and shapedbefore said core undergoes distortion and collapses; said 1.4percentages of said resin mix and said refractory material being basedon the total weight of those materials and the remaining percentagesbeing based on said resin mix.

10. The method of producing foundry cores as defined in claim 9 whereinsaid catalyst is selected from the group consisting of benzoyl peroxide,lauroyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide andt-butyl hydroperoxide, said accelerator is selected from the groupconsisting of cobalt naphthenate, cobalt octoate, manganese naphthenateand manganese octoate, and said promoter is selected from the groupconsisting of dimethylaniline, diethylaniline, N,N-dimethyl-p-toluidineand N,N- dimethyl-o-toluidine.

11. The method of producing foundry cores which does not necessitate theuse of heat comprising: admixing up to about 6% of polymerizable resinmix containing ethylenically unsaturated polyester resin formed from thereaction of an unsaturated polycarboxylic acid and polyhydric alcoholand monomeric, ethylenically unsaturated, polymerizable cross-linkingagent, and at least about 0.3% of acyl peroxide catalyst with about99.594% of refractory foundry core material; packing the resultingadmixture into a core box; and propelling at least about 0.18% of avapor phase N,N-dialkyl tertiary monoamine polymerization promoter freeof nitro and nitroso groups into said resulting admixture to form ahardenable foundry core mix that hardens at room temperature into ahard, self-supporting, porous foundry core against which molten metalmay be poured and shaped before said core undergoes distortion orcollapses; said percentages of said resin mix and said refractorymaterial being based on the total Weight of those materials and theremaining percentages being based on said resin mix.

12. The method of producing foundry cores as defined in claim 11 whereinsaid catalyst is selected from the group consisting of benzoyl peroxide,lauroyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide andt-butyl hydroperoxide, and said promoter is selected from the groupconsisting of dimethylaniline, diethylaniline, N,N-din1ethyl-p-toluidineand N,N-dimethyl-o-toluidine.

References Cited by the Examiner UNITED STATES PATENTS 1,831,555 11/31Earl 260-40 XR 2,480,928 9/49 Hurdis 260-454 2,751,775 6/56 Sergovic260-40 XR 2,895,935 7/59 Archer et al. 22193 2,898,259 8/59 Wheelock26040 XR 2,930,089 3/60 Emblem 22-1-93 FOREIGN PATENTS 531,968 10/16Canada.

5 MICHAEL V. BRINDISI, Primary Examiner.

MARCUS U. LYONS, Examiner.

UNITED STATES PATENT OFFICE EERTlFlCATE 0F CORRECTION Patent No.3,179,990 April 27, 1965 Stephen B. Freeman It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as correctedbelow.

Columns 5 and 6, Table II, first column, line 6 thereof,

for "cabalt" read cobalt columns 7 and 8 Table IV, first column, lines 1to 4 thereof, for "A", "B", "C", and "D", respectively, read E P G and Hrespectively; column 7, lines 71- and 72, for "dimethly" read dimethylcolumn 9, line 68, for "values" read valves column 10, line 14, for."on"read in line 32, for "develope" read develop column ll, line 30, for"0'. 8%"

read 0,3% column 14, line 53, for "10/16" read 10/56 Signed and sealedthis 30th day of November 1965..

(SEAL) Arrest:

ERNEST W.a SWIDER EDWARD J. BRENNER Amrsring Ufficer Commissioner ofPatents

1. THE METHOD OF PRODUCING FOUNDRY STRUCTURES WHICH COMPRISES: FORMING AFOUNDRY CORE MIX WITH A MIXTURE OF ABOUT 99.5-94% OF REFRACTORY FOUNDRYMATERIAL AND UP TO ABOUT 6% OF POLYMERIZABLE RESIN MIX CONTAININGETHYLENICALLY UNSATURATED POLYESTER RESIN FORMED FROM THE REACTION OF ANUNSATURATED POLYCARBOXYLIC ACID AND POLYHYDRIC ALCOHOL AND MONOMERIC,ETHYLENICALLY UNSATURATED, POLYMERIZABLE CROSS-LINKING AGENT, AT LEASTABOUT 0.8% OF PEROXIDE POLYMERIZATION CATALYST THAT IS SOLUBLE IN SAIDRESIN MIX, A POLYMERIZATION ACCELERATOR WHEN SAID CATALYST DOES NOTINCLUDE ACYL PEROXIDE, SAID ACCELERATOR, BEING IN THE FORM OF A SOLUBLEORGANIC SALT WHICH PROVIDES AT LEAST ABOUT 0.025% METAL IN AN ACTIVESTATE THAT INDUCES ACCELERATION OF THE POLYMERIZATION OF SAID RESIN MIX,AND AT LEAST ABOUT 0.18% OF VAPOR PHASE N,N-DIALKYL TERTIARY